1. Field
The embodiments described herein relate generally to a dental positioning system for electronic and film x-ray examinations, and more particularly to a dental positioning system arranged to center dental films and electronic x-ray sensors with a radiation source.
2. Description of Related Art
Intra-oral radiographs, i.e., “x-ray images”, are an important aspect of dental care. Such x-ray images have many uses, including diagnosing cavities and lesions, documenting treatment, and assisting in guiding procedures, among other things. X-ray images may be taken using a receptor to receive x-ray radiation emitted from an x-ray radiation source. Such a receptor may include either x-ray sensitive film or an x-ray sensitive electronic image sensor, such as a digital image sensor.
In the specific case of digital x-ray imaging, a solid state image sensor (such as, for example, an image sensor comprising a charge-coupled device (CCD) or a CMOS active pixel sensor array (APS)) is used as the receptor instead of x-ray film. Such sensors are typically 5-6 mm thick, and often have a cable for communication to a processing unit, such as a computer. Electronic sensors, unlike pieces of film, are re-usable, and are usually covered by a cross-infection barrier, such as a sheath.
Dental intra-oral image receptors are made in several standard sizes. The receptor is positioned in the mouth behind teeth so as to be positioned incident to x-ray radiation emitted from the x-ray radiation source. For example, in many applications it is desirable for the receptor to be positioned substantially perpendicular to the x-ray radiation. If the receptor is not placed and aligned correctly in the patient's mouth, clinically usable x-ray images may not be obtained, which may result in having to take additional x-rays with a corrected receptor alignment. Repeated x-ray images are undesirable because of the additional time, labor, material (in the case of film receptors) and increased exposure of the patient's mouth to radiation.
Although prior art techniques and devices may have the capability to achieve usable x-ray images, there are several problems with existing dental x-ray positioning systems, with respect to both film and electronic receptors, which are not addressed adequately by these techniques. Because accurate positioning of the receptor is difficult, several devices have been proposed to assist dental practitioners, such as dentists and hygienists, in placing and aligning the receptor.
At least one typical dental x-ray positioning system includes three separable pieces: a grip to hold the receptor, which typically has a bite block area, referred to as a bite block; a metal arm, which extends from the grip; and an alignment ring, which attaches to the metal arm from an end of the arm opposite the grip. When positioned in the mouth of a patient, the arm and the alignment ring generally protrude from the mouth and give the practitioner an alignment point on the alignment ring so that the practitioner can position the x-ray radiation source with respect to the positioning system.
An example of such a typical positioning device, which is configured specifically for a digital sensor receptor, is model XCP-DS digital sensor holder, manufactured by Rinncorp. Each XCP-DS digital sensor holder consists of a sensor grip, which includes a bite block upon which a patient can bite down to hold the grip in place in the mouth, a metal arm which has a generally square shaped cross section, and an attachment which has a complimentary square shaped opening to receive the square metal arm. The three pieces of the digital sensor holder are color coded to match together as a group. Each color corresponds to a specific radiographic view, such as bitewing, anterior, posterior, etc. Thus, a practitioner, such as a dental hygienist, seeking to assemble the digital sensor holder for bitewing x-rays will assemble the three color coded pieces together corresponding to bitewing x-rays.
One deficiency of arrangements like the aforementioned model XCP-DS digital sensor holder is that the square shaped opening in the alignment ring that receives the arm permits the practitioner to easily misalign the grip with respect to the attachment since the square opening will receive the arm in any of four, equally spaced, rotational positions. Moreover, because all of the arms of the model XCP-DS digital sensor holder share the same square cross section, a practitioner can physically couple parts of one color, corresponding to one radiographic view, with those of another color, corresponding to a different radiographic view, which may result in the sensor being misaligned with the x-ray source. Moreover, to obtain the various types of x-ray images, multiple three-piece combinations of grip-arm-attachment must be autoclaved, stored, and assembled for use by the practitioner. Often multiple x-rays are taken during a typical dental examination. Thus, the practitioner must be able to carefully assemble the three-piece combination repetitively while ensuring that the parts are properly aligned and not mismatched for the desired radiographic views.
One attempt to address misalignment of the receptor with respect to the x-ray source is described in U.S. Pat. No. 5,327,477 (Levy). Levy describes an x-ray film positioning system shown in FIG. 1A that includes a carrier and a sighting ring that receives the carrier. Annotations are displayed on the sighting ring corresponding to holes in the ring as well as corresponding carriers received in those holes. The film is placed on the carrier as shown in FIG. 3, and is held between a frictional support member and a film support plate. With the film loaded on the carrier, the carrier is inserted into its corresponding annotated hole in the sighting ring so as to position the film within a projection of a window of the ring.
However, one of ordinary skill in the art will appreciate that the arrangements described in Levy do not ensure that the film will be centered with respect to the film support plate, and thus there is no assurance that the film will be centered with the window of the sighting ring. Accordingly, if the film is not centered with the film support plate, even if the carrier is inserted into its corresponding hole in the ring, the film will not be centered with the x-ray source, and, therefore, the x-ray image produced will be off-centered, resulting in the need to take further x-rays, which, as noted above, generally is not desirable.
Thus, conventional positioning devices are prone to causing error in a clinical environment.